Donaldson and Scheffler have collaborated on many titles; some feature cameos from various titles - this blog attempts to list them all.
If you spot any, please leave us a comment!
I think some characters from "Room on a Broom" appear in "Smartest Giant in Town". There's a drawing of a witch on the wall on the first page, and on the following page, where George is buying some new clothes, there is a Dragon in the picture hanging above the door
Thanks Alison - we'll check it out, about time we sat down and added some more (as we have spotted since last blogging) :)